1. Field of the Invention
The present invention is related to a connector (an electrical circuit connecting element), and, in particular, a connector with an electromagnetic interference (hereinbelow, referred to as noise) absorbing means incorporated therein.
2. Discussion of the Background
FIG. 12 is a perspective view showing an example of a conventional connector. FIG. 13 is a perspective view showing the essential portion wherein the conventional connector is mounted on a printed circuit board 42.
In FIG. 12, reference numeral 20 designates a conductor for connection. Reference numeral 21 designates an insulating covering (i.e., a sleeve) which is used when two electrical circuits are connected as shown in FIG. 13.
With a desire of obtaining a noise eliminating effect when the circuit connection between terminals 30a and 30b of a circuit pattern is made on a printed circuit board 42 and the like as shown in FIG. 13, the following structures have been utilized;
One conventional structure incorporates a noise filter element in a terminal connecting pin 24 to a position adjacent its leading end, the noise filter element comprising ferrite beads 23 embedded in an insulating member 26 as shown in Figure 14 (a first example). Another structure incorporates a noise filter instead of the ferrite beads 23, the noise filter comprising a lead-through capacitor 22 and an earthed lead 25 as shown in FIG. 15 (a second example).
Now, the function/operation of such noise filters will be explained. Signals are sent or received between circuits of a device through the connecting pin 24. Since a noise component included in the signals is absorbed by the ferrite beads 24 or the lead-through capacitor 22, the connecting pin can eventually function as a noise filter.
FIG. 16 is a perspective view of a third example of the noise filter element wherein the first and the second example are combined to have the capacitor 22 and ferrite beads 23. As shown in FIG. 17, the filter noise element of FIG. 16 can be connected to the conventional ordinary type of connector of FIG. 12 to eliminate conduction noise. In FIGS. 16 and 17, reference numerals 24, 24a, 24b and 25 indicate terminals.
FIG. 18 shows an equivalent circuit of the circuit shown in FIG. 17. Specifically, a signal which has been transmitted from the terminal 30 is transmitted to the terminal 24a through the connector 20, and a noise component included in the signal can be eliminated by the capacitor 22 and the equivalent inductance 23a given by the ferrite beads 23. Then, the signal is output from the terminal 30b.
In addition, FIG. 19 is a connection diagram showing an example of an AC plug with a noise filter as an application example of this type of connector.
In FIG. 19, reference numeral 40 designates an AC cable. Reference numerals 41a, 41b and 42 designate a pair of AC plug pins and a connecting terminal pin, respectively. Reference numeral 43 designates a pair of capacitors. Reference numeral 44 designates a choke coil. The AC plug has such structure that the members 40-44 are molded in an insulating plug body 45 as a connector main body.
Noise which has come from the AC plug pins 41a or 41b is absorbed by an LC filter which is constituted by the choke coil 44 and the capacitors 43, and then is transmitted to the side of the AC cable 40.
Since the conventional methods for eliminating conduction noise requires the structure as mentioned above, a number of different kinds of electrical parts must be utilized in the conventional noise eliminating structures in order to realize both electrical connection and noise elimination. In particular, the third conventional example (FIGS. 16 and 17) has a disadvantage in terms of mounting space and economy. The conventional fourth example (FIG. 9) in the form of an AC plug has disadvantages in that it is bulky and heavier, and it is not suitable for mass production. In addition, these conventional devices have a disadvantage in that they are of little effect with respect to radiation noise.